Question

1) Tìm x , biết :

a) (2x+10)(x²+3)=0

b)-12(x-5)+7(3-x)=5

d)\(\left|2x-5\right|\)=13

Answer 1

a) (2x+10)(x²+3)=0

(1) 2x+10=0 (2) x²+3=0

=> 2x=0+10 =>x²=0-3

=> 2x=10 =>x²=-3(Loại)

=>x=10:2

=>x=5

Vậy x=5

Answer 2

b)-12(x-5)+7(3-x)=5

-12.x+12.5+7.3+7.(-x)=5

-12.x+60+21+7.(-x)=5

-12.x+60+21+(-7).x=5

[(-12)+(-7)].x+60+21=5

-19x+81=5

-19x=5-81

-19x=-76

x=-76:(-19)

x=4

Vậy x=4.

Answer 3

| 2x - 5 | = 13

=> 2x - 5 = -13

Hoặc 2x - 5 = 13

+) 2x - 5 = -13

2x = ( -13 ) + 5

2x = -8

x = ( -8 ) : 2

x = -4

+) 2x - 5 = 13

2x = 13 + 5

2x = 18

x = 18 : 2

x = 9.

Vậy x=-4 hoặc x=9